A little stress is normal in our daily life which can be good, as overcoming stress can make us more resilient. But when stress is severe or chronic such as breakdown of relationship, death in the family, domestic violence…, it can cause deleterious physical and psychological consequences on the body.

Stress is the common risk factor of 75%-90% of diseases with significant morbidity and mortality such as cardiovascular disease (hypertension, atherosclerosis, ischaemic heart disease), metabolic disease (diabetes, fatty liver), psychotic and neurodegenerative disorders (depression, Alhzeimer’s disease, Parkinson’s disease) and cancer (Cohen et al, 2007).

When the body is exposed to stress, it goes into a “fight and flight response” that is crucial for life threatening situation.

Stress activates the hypothalamic-pituitary-adrenal axis and the autonomic nervous system causing the release of neurotransmitters, hormones such as cortisol, adrenaline..

The increase of Cortisol increases the production of glucose, boosts energy to large muscles while inhibiting the production of Insulin and causes narrowing of blood vessels to force the blood to pump harder.  The increase of Adrenaline increases heart rate, respiratory rate to push more Oxygen to muscles. Whereas the non essential functions for an emergency response such as the immune system and digestion are suppressed. Stress decreases lymphocytes, white blood cells of the immune system so the body may be at a higher risk of having viral infections like common cold..

Chronic stress and Inflammation

Inflammation is the body response to a threat from a foreign invader, bacteria, virus, cancer cells or psychological or emotional stressor. Normally the white blood cells will concentrate in the area of injury and release chemicals called cytokines to fend off invaders, a process known as inflammation. Under normal circumstances, the inflammation process is naturally stopped in the body when the stress hormone cortisol level begins to rise. It is harmful to the body when inflammation does not stop as it should.  White blood cells of stressed people were found to be less responsive to Cortisol so the cells keep producing cytokines.

There is evidence that stress can activate inflammatory response in the brain as well as in the periphery. Stress induces chronic low grade inflammation which is the common factor contributing to a wide variety of chronic diseases (Rheumatoid arthritis, cardiovascular diseases, inflammatory bowel disease, depression…)

Chronic stress and the brain

The brain is normally protected from the circulatory molecules by a blood brain barrier. But under repeated stress, this barrier becomes leaky and circulatory inflammatory proteins can get into the brain.

Stress has many effects on the human nervous system and can cause structural changes in different parts of the brain. It can lead to atrophy of the brain mass and decrease its weight (Sarahiar et al- 2014).  There could be a decrease number of neurons, a reduce neurogenesis and atrophy of the hippocampus, the amygdala and the temporal lobes…

If we are in a dangerous or a highly emotional situation the amygdala that governs the survival instincts may take over, leaving other parts of the brain that help to store memory or perform other higher order tasks with less energy and ability to get the job done. The brain is shunting resources because it is in a survival mode and not memory mode. Therefore, we are forgetful or experience memory lapses during traumatic events.

-      Memory is one of the important functional aspects of the central nervous system. Short term memory is dependent on the function of the frontal and parietal lobes while long term memory depends on the function of large areas of the brain. The conversion of short term to long term memory and the total function of memory are dependent on the hippocampus. The hippocampus has the highest density of glucocorticosteroid receptors and also represents the highest level of response to stress. The amygdala is important in assessing the emotional experience of memory.

Chronic stress therefore has negative effects on learning and memory. Under special conditions, stress can temporarily improve the function of the brain and memory such as having a written examination can improve memory for a short period of time.

-      Cognition is the mental process of acquiring knowledge and comprehension through thoughts, experiences and from the senses. The cognitive processes include thinking, learning, decision making, judgement and problem solving. Similar to memory, cognition is mainly formed in the hippocampus, amygdala and temporal lobes. Mild stress facilitates an improvement in cognitive function but chronic or severe stress causes a reduction in spatial memory and verbal memory and activates neurodegenerative processes with reduction of cognition, reaction time, behavioural and mood disorders.

-      Mood and behaviour: chronic stress can change chemicals in the brain which modulate cognition and mood such as Serotonin that is important in mood regulation and wellbeing. Depression can impair cognition in planning and problem solving in emotional and social areas. High level of cortisol can interfere with sleep.

Stress and the Immune system

Stress causes impaired immunity and the person is prone to more frequent illnesses. Natural or synthetic glucocorticosteroids are known as anti-inflammatory drugs and immune suppressants. Severe stress can lead to malignancy by suppressing the immune system (Reiche et al-2004). It can decrease the activity of cytotoxic T lymphocytes and natural killer cells and lead to growth of malignant cells, genetic instability and tumour expansion.

Stress and the cardiovascular system

Stress whether acute or chronic has deleterious effect on the function of the cardiovascular system. The activation of the sympathetic nervous system increases the heart rate, blood pressure, causes vasoconstriction and can modulate the endothelial wall function and increase the risk of thrombosis and ischaemia as well as increase platelet aggregation (Rozanski et al, 1999).  This can cause vascular changes, atherogenesis , cardiac arrhythmias and subsequently myocardial infarction.

Stress and the respiratory system

People with stress can present with shortness of breath, rapid breathing as the airway can constrict especially in those with pre-existing chronic airways disease and asthma. Hyperventilation can bring on panic attacks.

Stress and the gastro-intestinal system

The brain and the gut are connected and are in constant communication. In fact, more neurons are in the gut then in the entire spinal cord according to a research published in the book Neuroscience. Some consider it as “a second brain”.  The gut is controlled in part by the central nervous system in the brain and spinal cord but it has its own network of neurons in the lining of the gastrointestinal system known as the enteric or intrinsic nervous system.

Stress affects appetite and prevents stomach emptying. It can cause indigestion, bloatedness, nausea, heartburn, diarrhea or constipation.

In serious cases, stress can cause a decrease in blood flow and oxygen to the stomach. Intense stress can cause a rare case of oesophageal spasm that can be mistaken for a heart attack. Stress can also be associated with changes in gut bacteria which in turn can influence mood. Stress can aggravate Irritable Bowel syndrome and Inflammatory Bowel disease.

Stress and the musculoskeletal system

Stress can cause muscle tension and in chronic stress the muscles tense up for a prolonged period of time and may trigger headache, migraine, jaw pain due to chronic spasm of neck, head, shoulder and jaw muscles. The muscle tension can eventually lead to muscle atrophy from disuse of the body.

Stress and the Reproductive system

Stress can cause low sex drive, erectile dysfunction in men, menstruation irregularities and can lead to fertility problems.

 

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